Science project

Salt Water Density

Difficulty of Project

Less than $5.00 

Safety Issues

To prevent drowning, young children should not be left unattended around water   

Material Availability

Readily available or easily purchased at a grocery store 

Approximate Time Required to Complete the Project

Less than 30 minutes to collect the data; one day to prepare the science fair display. 


To investigate the density of salt water 

Materials and Equipment

  • Large, clear jar
  • Egg
  • Water
  • Salt
  • Measuring spoons   

Background Information

Prior to starting this investigation, review the concepts of sink and float. Two factors affect an object’s ability to sink or float: density and buoyancy. An object sinks because it is denser or heavier than the water. Adding salt to the water causes the water to become denser.  

In this investigation, the egg floats in the salt water because the salt water is denser than the egg.  

Terms, Concepts, and Questions to Start Background Research


density: how heavy something is for its size 

buoyancy: the force that causes something to float  


Salt water is denser than fresh water. Because of its density, things float more easily in salt water. 

Research Questions
  • Why do some things float and some things sink?
  • Is it possible to make an egg float? 

Experimental Procedure

  1. Gather the necessary materials.
  2. Fill the jar with about ¾ full with water.
  3. Carefully place the egg in the water. Observe and record results.
  4. Remove the egg from the water. Add one tablespoon of salt to the jar of water.
  5. Carefully place the egg in the water. Observe and record the results.
  6. Continue to repeat steps 4 and 5 each time adding an additional tablespoon of salt until there is a noticeable change. Observe and record the results after each addition of salt.  



“Density and Buoyancy: Making Eggs Float” at 

“Principle of Buoyancy” at 

“Buoyancy Basics” at 

“Float, Sink or Swim” by Anne Hance at, 1994

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Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.

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